1. Field of the Invention
The present invention relates to acylated .gamma.-cyclodextrins, to a process for their preparation and to their use.
2. The Prior Art
Cyclodextrins are cyclic oligosaccarides which are assembled from 6, 7 or 8 .alpha.(1-4)-linked anhydroglucose units. The .alpha.-cyclodextrins, .beta.-cyclodextrins or .gamma.-cyclodextrins prepared by the enzymic conversion of starch differ in the diameter of their cavity. They are generally suitable for enclosing numerous hydrophobic foreign molecules of varying size.
However, with its solubility of 18.7% by weight, native .gamma.-cyclodextrin (.gamma.-CD) is comparatively poorly soluble in water and its capacity for solubilizing is also comparatively low. Thus, for example, U.S. Pat. No. 4,764,604, column 1, last paragraph, columns 7/8 table, discloses that .gamma.-CD only solubilizes in the low range of concentrations and that the complexes frequently precipitate out at higher concentrations. U.S. Pat. No. 4,764,604 also discloses that the solubility and solubilizing properties of .gamma.-CD can be improved by ether formation. It is known that methyl-.gamma.-CD is highly soluble in water and possesses average solubilizing properties. While hydroxpropyl-.gamma.-CD derivatives exhibit good hemolyzing properties, they only have average solubilizing properties. An additional disadvantage of .gamma.-CD ethers such as those mentioned by way of example is that they are difficult to degrade biologically.